Wave focusing antenna



Q33 iii mum mmnmwfi mimmm mu 1961 w. F. BAILEY 2,996,717

WAVE FOCUSING ANTENNA Filed Feb. 6, 1959 TO RECEIVER PROPAGAT|ON DIRECTION United States Patent 2,996,717 WAVE FOCUSING ANTENNA William F. Bailey, Valley Stream, N.Y., assignor to Hazeltine Research, Inc., Chicago, 11]., a corporation of Illinois Filed Feb. 6, 1959, Ser. No. 791,773 5 Claims. (Cl. 343788) General This invention relates to antenna systems and, particularly, to such antenna systems of the type for focusing a received electromagnetic wave on a pickup device.

This application is a continuation-in-part of application Serial No. 498,077 filed March 30, 1955, now abandoned. Antenna systems previously proposed for focusing electromagnetic waves on a pickup device have employed a plurality of mechanical elements for slowing down the various portions of the wave to achieve the desired focusing. Such systems are more cumbersome and complex than is desirable for many applications.

It is an object of the invention, therefore, to provide a new and improved antenna system for focusing received electromagnetic waves on a pickup device.

In accordance with the invention, an antenna system comprises a rod means of material having a high permeability-permittivity product for focusing at one end of the rod an electromagnetic wave incident at the other end of the rod so that the field components of the wave are directed in opposite directions through adjacent crosssectional areas. The antenna system also includes a pickup device having portions so wound that a first portion is responsive to only the variations in the focused field of the first component of said wave for developing corresponding electrical voltage variations and a second portion is responsive to only the variations in the focused field of the second component of said wave for developing corresponding electrical voltage variations.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

The single figure of the drawing shows an antenna system constructed in accordance with the present invention.

Description of antenna system Referring to the drawing, the antenna system there represented comprises a rod 11 of, for example, ferrite material for concentrating at one end 12 of the rod 11 the field components of an electromagnetic Wave incident at the other end 13 of the rod and propogated in the direction of the axis of the rod. The ferrite rod 11 is preferably forked at one end into a pair of tines 15 and 16 so that, for example, the magnetic-field component of an electromagnetic wave may be concentrated therein.

The antenna system further includes a pickup device, for example, a pickup coil 20 disposed adjacent the firstmentioned end 12 of the rod and responsive to variations in the concentrated field components for developing corresponding electrical voltage variations across the terminals 21, 21 of the pickup device. The pickup coil 20 is preferably interwoven around the fork tines 15 and 16 so that the coil 20 has a first portion 22 encircling the tine 15 in a clockwise sense and has a second portion 23 encircling the other time 16 in a counterclockwise sense, the coil portions 22 and 23 being responsive to variations in, for example, the concentrated magnetic-field component for developing corresponding electrical voltage variations which combine in an additive manner to produce increased voltage variations across the terminals 21, 21 of ice the pickup coil 20. Where it is desired to utilize the electric-field component instead of the magnetic-field component, the pickup device may comprise suitable pickup electrodes disposed adjacent the end 12 of the rod.

Operation of antenna system Considering the operation of the antenna system just described, ferrite is a polycrystalline substanw composed of metallic oxides and ferric oxide. As a result, ferrite materials have relatively high permeability factors t ranging to about 1000 in some cases and have relatively high permittivity factors or dielectric constants e of the order of 10-20. As a result, the velocity of electromagnetic waves when propagated through a ferrite material is considerably less than the velocity of such waves in free space. The relationship between the velocity of propagation in a material and the velocity of propagation in free space is where v denotes the velocity of propagation in the material 0 denotes the velocity of propagation in free space [.L denotes the permeability of the material e denotes the permittivity or dielectric constant of the material For a typical ferrite material, the permeability ,u is 500 and the permittivity e is 10. Inserting these values into the above relationship indicates that the velocity of propagation in such ferrite material is 0.014 time the velocity in free space. Thus, it appears that the velocity of an incident electromagnetic wave is considerably reduced upon entering a region of such material.

Because of the decrease in velocity of an electromagnetic wave in a region of ferrite material, a rod of such material may be used to focus the field components of such electromagnetic wave. Considering, for example, the magnetic-field component 18 of an incident electromagnetic wave as indicated in the drawing, as a given wave front of the electromagnetic wave passes down the axis of the rod, the magnetic-field component 18 within the rod is progressively slowed down with respect to the corresponding portion of the magnetic-field component without the rod. In this manner, the magnetic-field component within the ferrite rod 11 is distorted as indicated in the drawing so as to concentrate or focus the magneticfield component in the tines 15 and 16 of the rod 11.

By suitably winding a pickup coil around the tines 15 and 16 as indicated by the coil 20, variations in the magnetic-field component corresponding to the transmitted signal variations induce corresponding voltage variations in the coil portions 22 and 23 which combine in an additive manner to produce increased voltage variations across the terminals 21, 21. These terminals may be coupled to any suitable utilization device such as, for example, a radio receiver.

It will be noted that the portion of the magnetic-field component 18 passing through the tine 15 is in a direction opposite to the portion of the magnetic-field component 18 passing through the tine 16. As a result, the portion 22 of the coil 20 must be wound around the tine 15 in, for example, a clockwise sense while the coil portion 23 is wound around the time 16 in, for example, a counterclockwise sense. In this manner, the voltage variations in the coil portions 22 and 23 are combined in an additive manner so as to produce a resultant increased voltage variation across the coil terminals 21, 21.

It should be understood that while ferrite appears to be especially useful for the purposes of the invention because of its high permeability and permittivity, other materials having that property will probably occur to those skilled in the art after having read the foregoing and such other materials may, Where desired, be used in place of ferrite.

From the foregoing description of the invention, it will be apparent that an antenna system constructed in accordance with the present invention represents a new and improved antenna system for focusing received electromagnetic waves on a pickup device.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore. aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An antenna system comprising: a rod means of material having a high permeability-permittivity product for focusing at one end of the rod an electromagnetic wave incident at the other end of the rod, so that the field components of the wave are directed in opposite directions through adjacent cross-sectional areas; and a a pickup device having portions so Wound that a first portion is responsive to only the variations in the focused field of the first component of said wave for developing corresponding electrical voltage variations and a second portion is responsive to only the variations in the focused field of the second component of said Wave for developing corresponding electrical voltage variations.

2. An antenna system comprising: a ferrite rod means positioned with its longitudinal axis parallel to the direction of propagation of an electromagnetic wave for focusing at one end of said rod an electromagnetic wave incident at the other end of said rod, so that the field components of said Wave are directed in opposite directions through adjacent cross-sectional areas; and a pickup device having portions so wound that a first portion is responsive to only the variations in the focused field of the first component of said wave for developing corresponding electrical voltage variations and a second portion is responsive to only the variations in the focused field of the second component of said wave for developing corresponding electrical voltage variations.

3. An antenna system comprising: a ferrite rod means positioned with its longitudinal axis parallel to the direction of propagation of an electromagnetic wave for focusing at one end of the rod the magnetic-field portion of an electromagnetic wave incident at the other end of the rod, so that the magnetic-field components of the wave are directed in opposite directions through adjacent crosssectional areas; and a pickup coil having portions so Wound that a first portion is responsive to only the variations in the focused magnetic-field portion of the first component of said Wave for developing corresponding electrical voltage variations and a second portion is responsive to only the variations in the focused magneticifield portion of the second component of said wave for developing corresponding electrical voltage variations.

4. An antenna system comprising: a rod of material having a high permeability-permittivity product and forked at one end for concentrating in the fork tines the magnetic-field component of an electromagnetic wave incident at the other end of the rod and propagated in the direction of the axis of the rod; and a pickup coil interwoven around the fork tines and responsive to variations in the concentrated magnetic-field component for developing corresponding electrical voltage variations across the terminals of the pickup coil.

5. A ferrite rod antenna system comprising: a ferrite rod forked at one end into a pair of tines for concentrating in the fork tines the magnetic-field component of an electromagnetic wave incident at the other end of the rod and propagated in the direction of the axis of the rod; and a pickup coil having a first portion encircling one tine in a clockwise sense and having a second portion encircling the other tine in a counterclockwise sense, said portions being responsive to variations in the concentrated magnetic-field component for developing corresponding electrical voltage variations which combine in an additive manner to produce increased voltage variations across the terminals of the pickup coil.

References Cited in the file of this patent UNITED STATES PATENTS 1,020,032 Fessenden Mar. 12, 1912 1,641,925 Gabriel Sept. 6, 1927 2,375,593 Sontheimer et al. May 8, 1945 2,641,704 Stott June 9, 1953 2,695,384 Stuart Nov. 23, 1954 FOREIGN PATENTS 40,751 Denmark Aug. 29, 1929 OTHER REFERENCES Pub. I, Wavelength Lenses, Proceedings of the IRE,

vol. 36, No. 2, February 1948, pp. 206-212. 

